Many qualitative and quantitative diagnostic self-tests have developed in the clinical field utilizing bodily fluids from humans or animals as a sample. Many such devices have been developed for the analysis of blood glucose in humans. However, additional analytes may be found and the concentration determined if the appropriate low cost system was available.
One common means for the determination of an analyte in a body fluid sample is through the use of reflectance measurements using a spectrophotometer and test strip or by alternatively using a biosensor system. The biosensor system has been popular in more recent times because of the ability for a biosensor to use small sample sizes 3 to 5 .mu.ls where as traditional reflectance systems usually require substantially more sample in the range of 5 to 10 .mu.ls. However, the biosensor systems tend to be affected by numerous interference's found in the body fluid samples whereas, the reflectance measurements tend to be less affected and therefore provide more accurate results.
The need for a low cost system which permits low volume sample size utilization and accurate results is important to the diagnostic field and could make the monitoring of chronic disease applications more achievable.
The National Institute of health conducted a large scale study to evaluate the benefit of long term tight control of blood glucose monitoring. The study known as the DCCT proved that long term tight control of the blood glucose levels in patients with diabetes had a direct relationship to the health of the patient. One way for the medical profession to monitor the control of their patients is through the use of low cost, convenient monitors with memory.
Many diabetics currently use a test method described in U.S. Pat. No. 5,304,468 to Phillips et al. This system is comprised of an electronic meter and disposable dry reagent test strip. The meter reads the color change of the test strip after the blood sample has been applied and converts this to an approximate reading of the concentration of glucose in the blood sample. The test strips have some variation to them and the patient must select the appropriate calibration level prior to using the test strip to monitor their blood. In this way the meter can accommodate various strip performance issues. The system also uses a complex dual optics system to resolve the reflectance reading.
U.S. Pat. No. 4,637,403 to Garcia et al. Describes an integrated system which provides a method by which the patient lances the finger to get a sample of blood which is then used by the device to provide a reading of the blood glucose or other analyte concentration. This system uses a complex reflectance system to read the analyte level in the sample.
U.S. Pat. No. 5,279,294 to Anderson et al. Describes a hand held shirt pocket device for the quantitative measurement of glucose in a blood sample. The device uses sophisticated optics and test strip system to achieve a reading.
U.S. Pat. No. 5,515,170 to Matzinger et al. Describes at the difficulties of keeping a reagent test strip aligned with an optics system.
European Patent Specification 0 351 891 B1 Hill et al. Describes an electrochemical sensor system and electrodes which are suitable for measuring the concentration of an analyte in a body fluid sample. The system requires the use of expensive electrodes and reader to determine the analyte concentration level.
U.S. Pat. No. 4,994,167 to Shults et al. Describes a measuring device for determining the presence and amount of a substance in a biological fluid using electrochemical means.
U.S. Pat. No. 5,580,794 to Allen et al. Describes a single use disposable-measuring device for determining the presence and amount of a substance in a biological sample using reflectance methods. The system uses optics and electronics which are mated on a single plane.
U.S. Pat. No. 5,522,255 to Neel et al. Describes a fluid dose, flow and coagulation device which uses a non-volatile electronic calibration device to check the calibration of the reagent strip.
U.S. Pat. No. 5,053,199 to Keiser et al. describes a biosensing meter with a pluggable memory key. This device uses a plugable memory key to control the operations of the meter.
The above patent disclosures are incorporated herein by reference in their entirety.
Although many improvements have been made, the cost and complexity needed to read the analyte concentration of a body fluid is still significant. The need to match calibration of a meter to the strips and the system of holding a test strip in alignment with the optics has been problematic and led to numerous errors in analyte concentration readings.
Currently, existing calibration mechanisms require the loading of a calibration chip, strip or manually inputting a calibration code into the meter. These devices can be reused numerous times resulting in errors by the patient who do not chance or enter the appropriate calibration data.
In addition, a system which requires a smaller body fluid sample would make it more convenient for the patient and coupled with the improved accuracy found in reflectance devices compared to electro chemical would make the monitoring simpler and more accurate.
An additional issue is the use of test strips which are out of date. Old test strips which are expired can lead to errors and inaccurate results. By providing a means to eliminate the use of expired test strips the patients will not have to monitor the expiration date of the test strips and eliminates patient errors from using old test strips.